If you want to sink a well in California and pump out as much water as you can, there historically hasn’t been a lot to stop you. Unlike other Western states, California has never regulated groundwater withdrawals. As a result, over the last 150 years, Californians have pumped nearly 160 cubic kilometers of groundwater from the Central Valley, the state’s agricultural heartland. That’s enough water to fill Lake Powell, Lake Mead, and all the Colorado River reservoirs downstream—twice, with some left over. MORE